1. Field of the Invention
The present invention relates generally to a mobile communication system, and in particular, to a method for managing mobility between heterogeneous networks using a neighbor graph (NG) in a mobile communication system comprised of IP-based (Internet Protocol) heterogeneous networks.
2. Description of the Related Art
Generally, a mobile communication system performs a handoff when a mobile node (MN) moves from a service area of a current access node (AN) to a service area of another access node.
In a single communication network, because user selectable service requirements are extremely restrictive and all access nodes are similar to each other in their characteristics, during handoff, an access node is selected considering only mobility of a user, instead of considering user requirements.
However, communication networks for mobile communication, wireless local area network (WLAN), and mobile Internet, which have been independently developed and commercialized, are expected to be integrated in a next generation communication environment along with the development of IP technology supporting mobility, such as Mobile Internet Protocol (IP).
Because heterogeneous networks have different characteristics and provide different types of services, in order to receive a desired service, a user must select a network suitable for requirements of the corresponding service.
In a communication environment where such heterogeneous networks coexist, when a handoff is performed considering only mobility, if a new access node fails to satisfy user requirement, a quality of service (QoS) abruptly deteriorates, and in order to receive a required QoS, a mobile node repeatedly performs handover, causing a ping-pong phenomenon. A handoff delay due to the ping-pong phenomenon further deteriorates the QoS (also known as a “service level”).
In a mobile communication network, neighbor graph (NG) is used as a technique for providing fast handoff between access nodes. Because a neighbor graph includes all latent movement paths in a wireless network, an access node can easily determine a possible handoff by searching the neighbor graph.
However, because an existing handoff method using the neighbor graph performs a handoff using only information on a neighbor access node in the same network, to which a mobile node is possibly handed off and does not consider operational situations of the access node, such as an available capability of the access node, it cannot support a seamless service based on a fast handoff in a real-time multimedia service that requires a wide available bandwidth.
Therefore, it is necessary to develop a neighbor graph technique that considers available capability of an access node for effective multimedia service and seamless handoff in a next generation mobile communication system based on heterogeneous networks.